1. Field of the Invention
This invention relates generally to insect and arthropod repellents and more specifically to mosquito, fly, tick and mite repellents using biologically based components.
2. Description of Related Art
At the present time, N,N,-diethyl-m-toluamide (DEET) is the active ingredient of most commercial topical insect repellents (see Table 1, below), and the current US Army insect repellent (EDTIAR) contains DEET as its active ingredient. The major commercial brands, Off!(copyright), xe2x80x9cDeep Woods Off!(copyright), and Cutter(copyright), are all DEET based products and comprise 85% of insect repellent sales (Consumer Reports Buying Guide, 1994 Special Year-End Issue). Consumer Reports tests indicated that products with the highest concentration of DEET lasted the longest against mosquitoes, but cautioned that excessive use of DEET could pose some risk, especially for children. Other disadvantages associated with DEET include: It is a synthetic chemical having a limited spectrum of activity and a noticeably unpleasant odor; DEET is a powerful plasticizer and will dissolve or mar many plastics and painted surfaces; DEET plasticizes the inert ingredients typically used in topical formulations in order to lengthen the time of effectiveness. This leads to DEET formulations with low user acceptability.
In recent years, a proprietary bath oil (Skin-So-Soft(copyright), Avon Products, Inc., New York) has been used as a topical insect repellent. Two of its ingredients (diisopropyl adipate and benzophenone) are repellent to Aedes aegypti (King, W. V. 1954. Chemicals evaluated as insecticides and repellents at Orlando, Fla. U.S. Dept. of Agriculture, Agriculture Handbook No. 69:1-397). However, the bath oil was reported as less effective and less persistent than DEET (Rutledge et al., 1982, Repellent activity of a proprietary bath oil (Skin-So-Soft), Mosquito News:42:557-559).
Efforts to develop a natural insect repellent have motivated studies of oils of citronella, turpentine, pennyroyal, cedarwood, eucalyptus and wintergreen, but these are relatively ineffective (Handbook of Nonprescription Drugs, 1993, 10th Ed., American Pharmaceutical Assn., Washington, D.C.). Consumer Reports tests indicated that xe2x80x9cnatural productsxe2x80x9d and products without DEET, including Skin-So-Soft(copyright), provided little or no protection against mosquitoes (Consumer Reports Buying Guide, 1994 Special Year-End Issue). Insect repellents for nonprescription oral use are not generally recognized as safe and effective (Federal Register, 1985, 50:25170).
Franz Bencsits describes xe2x80x9cUse of First Runnings Coconut Fatty Acid as Insect-repellentxe2x80x9d in U.S. Pat. No. 5,594,029. Although Bencsits does not describe specifically what xe2x80x9cfirst runningsxe2x80x9d of coconut fatty acids are, he describes that combining the xe2x80x9cfirst runningsxe2x80x9d with xe2x80x9c. . . another active substance, an oil or fat selected from the group consisting of rape-seed oil, sunflower oil, peanut oil/butter, . . . xe2x80x9d etc. provides an insect repellent. Because the term xe2x80x9cfirst runningsxe2x80x9d is not a term of art and is not understood by the average knowledgeable person working in the field, it is impossible to know exactly what substance Bencsits tested. The average knowledgeable person working in the field of formulating insect repellents does not know what xe2x80x9cfirst runningsxe2x80x9d are or how to obtain them. Many experts also do not understand this term and were not able to discover its meaning even with research. Furthermore, the limited number of tests and controls, and lack of attention to fatty acids as potential skin irritants appear to limit Bencsits"" invention to non-animal surfaces.
Bencsits teaches the use of up to 15% potassium hydroxide (KOH) in his formulations. KOH ionizes fatty acids, turning them into non-volatile salts. Bencsits thus teaches away from the utility of volatile compounds.
Bernard Crammer, et al. Describes in U.S. Pat. No. 5,064,859, a method for killing lice and lice eggs that have infested human skin and hair with a C8 to C12 alkyl radical. The patent does not mention repelling live approaching insects.
Stephen Herman describes, in U.S. Pat. No. 5,093,326, a composition comprising an ozonized derivative of unsaturated hydrocarbon for repelling insects from a surface. Performance does not appear competitive with DEET.
Clearly there is a need for a long-lasting effective insect repellent that is pleasant to use and that will not damage plastic containers, or the text printed on the containers.
It is an object of the present invention to provide an insect and arthropod repellent that is safe, long-lasting, effective and pleasant. It is a further object for the inventive formulation to avoid the damage to plastic containers and the text printed on the containers that is associated with currently effective insect repellent formulations.
The present inventive insect and arthropod repellent comprises a combination of two or more homologous volatile repellent molecules, similar or identical to those normally found on human skin, wherein at least one of the molecules has a vapor pressure between about 0.1 mm Hg and about 10 mm Hg at 125xc2x0 C. and at least one other molecule has a vapor pressure between about 5 mm Hg and about 100 mm Hg at 125xc2x0 C.